An operator of a viewing device may desire to adjust a line of sight while observing a scene through the viewing device. Many viewing devices may be adjusted so as to apply a specific angle of deviation to the image as viewed by the operator. For example, the impact point of a projectile as viewed by a day scope may be adjusted in angle so that it appears to be at the point designated by the day scope's reticle. The amount of adjustment changes when the day scope is used at different target ranges, or when the day scope is moved from one weapon to another. As another example, a clip-on night sight may be adjusted in the factory such that the apparent angular position of a point in the image as viewed by the sight is the same as that point's angular position in the output of the sight.
Certain types of sights have both day-vision and night-vision capability, and are referred to herein as “night-day sights.” Night vision capability is provided by a night-vision optical system, referred to hereinafter as “night optics.” Likewise, the day-vision capability is provided by a day-vision optical system, referred to hereinafter as “day optics.” Because night optics has different imaging capabilities than day optics and includes a night vision sensor, such as an image intensifier or thermal imaging sensor, the optical design of the night optics is different than the day optics. Accordingly, the night optics and the day optics are typically separate optical systems, even when combined in the same housing.
An adjustable wedge-prism assembly is disclosed in U.S. Pat. No. 7,142,357 (the '357 patent) to Greenslade, titled “Night-Day Boresight with Adjustable Wedge-Prism Assembly,” which is incorporated herein by reference. A boresight alignment device is disclosed in U.S. Pat. No. 7,359,114 (the '114 patent) to Sauter, et al., titled “Clip-On Night Vision Device,” which is incorporated herein by reference. The prior art methods and structures described in the '357 and '114 patents introduce appreciable degradation into the system, add considerably to the overall length and weight of the system, and/or require the complicated, non-intuitive rotation of multiple prisms or tilting groups of optical elements to accomplish alignment. These shortcomings may be unacceptable to an operator of the viewing device.
Accordingly, there is a need in the art for an improved line of sight adjustment device for use in an optical sighting device.